A Kinetic Investigation of the Mechanisms of Radiation-Induced Strand Breakage in DNA Model Systems
Time-resolved reductions in the light scattering intensity (LSI) of N2O or oxygenated aqueous solutions of single stranded homologous polynucleotides, following pulse irradiation, have been studied as indicies of strand breakage (s.b.) (for a review of the LSI method see Schnabel 1979). With doses of 3–24Gy/pulse, a number of kinetically distinct modes of breakage are apparent. For the polypyrimidines, poly C and poly U, these include i) a small proportion of fast strand breaks (τ½ = 50μs) arising from the direct action of OH-radicals at the sugar phosphate backbone, and ii) major, slower first order routes to breakage that proceed through base radical mediated pathways (Figure 1) (Lemaire et al. 1984).
KeywordsSugar Hydroxyl Adduct Thiol Macromolecule
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